Although the mechanism of action of modafinil was initially unknown, it now appears that the drug acts as a selective, relatively weak, atypical dopamine reuptake inhibitor. However, it appears that other additional mechanisms may also be at play.
Modafinil is also used off-label to treat sedation and fatigue in many conditions, including depression, fibromyalgia, chronic fatigue syndrome, myotonic dystrophy, opioid-induced sleepiness, spastic cerebral palsy, and Parkinson’s disease. Modafinil has been shown to improve excessive daytime somnolence and fatigue in primary biliary cirrhosis.
Modafinil is usually taken each morning to prevent daytime sleepiness, or 1 hour before the start of a work shift to treat work-time sleep disorders.
According to documentation distributed by Teva Pharmaceuticals, one-third of participants in clinical trials reported experiencing headaches; 11% reported nausea; other negative side-effects such as nervousness, diarrhea, insomnia, anxiety, dizziness, and gastrointestinal problems were reported by less than 10% of participants.